Computer assisted targeting device for use in orthopaedic surgery

• US 20010036245A1
• Filed: 06/18/2001
• Published: 11/01/2001
• Est. Priority Date: 02/10/1999
• Status: Active Grant

• Current Assignee: Stryker European Holdings I, LLC (Stryker Corporation)
• Original Assignee: GE Medical Systems Global Technology Company LLC (GE Healthcare Technologies, Inc.)
• Inventors: Kienzle, Thomas C. III, Lea, Jon T.
• Granted Patent: US 6,697,664 B2
• Time in Patent Office: Days
• US Class Current: 378/4
• CPC Class Codes: A61B 17/1703 using imaging means, e.g. by X-rays
• CPC Class Codes: A61B 17/1721 for applying pins along or parallel to the axis of the femoral neck
• CPC Class Codes: A61B 2017/00207 with hand gesture control or hand gesture recognition
• CPC Class Codes: A61B 2017/00902 transparent or translucent
• CPC Class Codes: A61B 2034/102 Modelling of surgical devices, implants or prosthesis
• CPC Class Codes: A61B 2034/107 Visualisation of planned trajectories or target regions
• CPC Class Codes: A61B 2034/2055 Optical tracking systems
• CPC Class Codes: A61B 2034/2068 using pointers, e.g. pointers having reference marks for determining coordinates of body points
• CPC Class Codes: A61B 2034/2072 Reference field transducer attached to an instrument or patient
• CPC Class Codes: A61B 2090/376 using X-rays, e.g. fluoroscopy
• CPC Class Codes: A61B 2090/3916 Bone tissue
• CPC Class Codes: A61B 2090/3983 Reference marker arrangements for use with image guided surgery
• CPC Class Codes: A61B 34/10 Computer-aided planning, simulation or modelling of surgical operations
• CPC Class Codes: A61B 34/20 Surgical navigation systems; Devices for tracking or guiding surgical instruments, e.g. for frameless stereotaxis
• CPC Class Codes: A61B 34/25 User interfaces for surgical systems
• CPC Class Codes: A61B 46/10 specially adapted for instruments, e.g. microscopes
• CPC Class Codes: A61B 6/12 Arrangements for detecting or locating foreign bodies
• CPC Class Codes: A61B 6/4233 using matrix detectors
• CPC Class Codes: A61B 6/4405 the apparatus being movable or portable, e.g. handheld or mounted on a trolley
• CPC Class Codes: A61B 6/4423 related to hygiene or sterilisation
• CPC Class Codes: A61B 6/547 : involving tracking of position of the device or parts of the device
• CPC Class Codes: A61B 6/548 : Remote control of the apparatus or devices
• CPC Class Codes: A61B 6/583 : using calibration phantoms
• CPC Class Codes: A61B 90/36 : Image-producing devices or illumination devices not otherwise provided for
• CPC Class Codes: A61B 90/361 : Image-producing devices, e.g. surgical cameras

Abstract

An image guided surgery system to enable a surgeon to move a surgical tool into a desired position relative to a body part is provided. The system works by accurately superimposing representations of the tool being used in the surgical field over images of the body part such that real-time tool position feedback is provided to the surgeon. The system uses a fluoroscopic x-ray device to generate two-dimensional body part images, a localizing device to determine the poses of surgical tools and the x-ray device, mathematical modeling of the imaging chain of the x-ray device, and a means for displaying the images of the body part superimposed with representations of the surgical tools. A related feature is the use of a digital flat-panel x-ray imager that employs a regular array of sensors to convert incident x-ray energy to a computer readable image, thereby permitting the fluoroscopic x-ray device to be used in any orientation without being affected by distortions due to local magnetic fields.

Claims

1. An image guided surgery system comprising:

an imaging device having an x-ray source and an x-ray receiver for generating a plurality of two-dimensional images of a body part;

a localizing device for determining the three-dimensional locations and orientations of the imaging device and a surgical tool;

an imaging model with imaging model parameters for modeling the projection and mapping of points between the x-ray source and the x-ray receiver of the imaging device to the images wherein the imaging model parameters are dependent on the orientation of the imaging device;

first means for determining first imaging model parameters while the imaging device occupies an orientation;

storage means for storing a set of the first imaging model parameters and corresponding imaging device orientation for a plurality of imaging device orientations; and

second means for determining second imaging model parameters corresponding to a given orientation of the imaging device and calculated from the set of first stored imaging model parameters and corresponding imaging device orientations;

wherein the imaging model and the second imaging model parameters for the given orientation permit accurate superposition of a representation of the surgical tool on the images of the body part.

2. The image guided surgery system of

claim 1

wherein the imaging device is a C-arm fluoroscope.

3. The image guided surgery system of

claim 1

wherein the x-ray receiver comprises a flat panel x-ray imager.

4. The image guided surgery system of

claim 3

wherein the flat panel imager is integral to the imaging device.

5. The image guided surgery system of

claim 3

wherein the flat panel x-ray imager is contained in a housing and said housing is attached to the imaging device.

6. The image guided surgery system of

claim 1

wherein the first means for determining the first imaging model parameters comprises:

a calibration grid having markers disposed in fixed and known locations, visible in x-ray images; and

means for determining the pose of the calibration grid relative to either the x-ray source or x-ray receiver;

wherein the calibration grid is held in one or more poses between the x-ray source and x-ray receiver.

7. An image guided surgery system with the set of first imaging model parameters of

claim 1

wherein appropriate second imaging model parameters for a given orientation are calculated by interpolation of a subset of the set of first imaging model parameters.

8. The image guided surgery system of

claim 3

wherein the imaging model parameters comprise conic projection model parameters and the first means for determining said conic projection model parameters comprises:

a calibration grid having markers disposed in fixed and known locations, visible in x-ray images; and

means for determining the pose of the calibration grid relative to either the x-ray source or x-ray receiver;

wherein the calibration grid is held in one or more poses between the x-ray source and x-ray receiver.

9. An image guided surgery system of

claim 2

wherein the x-ray receiver is a flat panel imager and the imaging model parameters comprise conic projection model parameters and the set of first imaging model parameters comprise a set of first conic projection model parameters wherein appropriate second conic projection model parameters for a given orientation during surgery are calculated by interpolation of a subset of the set of first conic projection model parameters.

10. The image guided surgery system of

claim 1

wherein the orientation of the imaging device is calculated relative to a horizontal plane.

11. The image guided surgery system of

claim 10

wherein the localizing device comprises a sensor unit, and said sensor unit is attached to a cart by a rigid support structure of known geometry and dimensions, such that the sensor unit'"'"'s orientation relative to the horizontal plane is known.

12. The image guided surgery system of

claim 10

wherein the localizing device comprises a sensor unit, and said sensor unit is attached to a cart by a rigid support structure of known geometry and dimensions and adjustable joints with rotary position encoders for measuring the angular position of each joint such that the sensor unit'"'"'s orientation relative to the horizontal plane is known.

13. The image guided surgery system of

claim 10

wherein the localizing device comprises a sensor unit and the orientation of the sensor unit relative to the horizontal plane is determined by an inclinometer mounted on said localizer sensor unit.

14. The image guided surgery system of

claim 10

wherein the orientation of the imaging device relative to the horizontal plane is calculated by inclinometers mounted on the imaging device.

15. The image guided surgery system of

claim 6

wherein the means for determining the pose of the calibration grid relative to the imaging device comprises a localizing device.

16. The image guided surgery system of

claim 6

further comprising a mounting means for holding the calibration grid in a fixed and known pose relative to the imaging device.

17. The image guided surgery system of

claim 1

wherein the imaging model parameters comprise mapping model parameters and the first means for determining said mapping model parameters comprises:

a calibration grid having markers, visible in x-ray images;

means for determining the positions of the markers in the x-ray images; and

means for determining the positions of the markers relative to the x-ray receiver;

wherein, the calibration grid is held in proximity to the x-ray receiver.

18. A method for accurately superimposing a representation of a surgical tool over images of a body part, comprising the steps of:

providing an imaging device with imaging model parameters that are dependent on the orientation of the imaging device;

positioning the imaging device in a plurality of orientations and measuring said orientations;

providing a calibration grid having markers disposed in fixed and known locations, visible in x-ray images;

using the imaging device to take an x-ray image of the calibration grid at each orientation of the imaging device, said x-ray image having shadows corresponding to the markers on the calibration grid;

calculating first imaging model parameters corresponding to each orientation of the imaging device by locating the shadows of the markers on the calibration grid in the x-ray image;

storing the first imaging model parameters with the corresponding measured orientation of the imaging device for the plurality of imaging device orientations;

positioning the imaging device relative to the body part and measuring the orientation of the imaging device;

using the imaging device to take an x-ray image of the body part;

calculating second imaging model parameters through interpolation of the stored first imaging model parameters based on the measured orientation of the imaging device;

determining the pose of the surgical tool relative to the imaging device;

mathematically projecting a computer representation of the surgical tool through the imaging model using the second imaging model parameters; and

superimposing the projected representation of the surgical tool on a displayed image of the body part.

19. The image guided surgery system of

claim 18

wherein the calculation of the first imaging model parameters and the storage of said first imaging model parameters and corresponding imaging device orientations is accomplished prior to a surgical procedure and the calculation of the second imaging model parameters corresponding to a given imaging device orientation is accomplished during the surgical procedure.

20. An image guided surgery system to enable a surgeon to move one or more surgical tools into a desired pose relative to a body part, comprising:

an imaging device for generating a plurality of images of the body part, the imaging device outfitted with localizing emitters;

one or more surgical tools outfitted with localizing emitters;

a localizing device comprising two or more sensor units, each with a coordinate frame and comprising a plurality of sensor elements, including a first sensor unit able to view and calculate the pose of the imaging device and a second sensor unit able to view and calculate the pose of the one or more surgical tools;

means for displaying representations of the one or more surgical tools relative to images of the body part; and

means for determining a relationship among the coordinate frames of the two or more sensor units.

21. The image guided surgery system of

claim 20

wherein the means for determining the relationship among the coordinate frames of the sensor units includes a registration object whose pose is measured by the sensor units.

22. The image guided surgery system of

claim 21

wherein the registration object is the imaging device.

23. The image guided surgery system of

claim 20

further comprising:

a surgical drape placed between the imaging device and the one or more surgical tools.

24. The image guided surgery system of

claim 23

wherein the means for determining the relationship among the coordinate frames of the sensor units includes a registration object whose pose is measured by the sensor units prior to the placement of the surgical drape.

25. A computer assisted surgery system to enable a surgeon to move one or more tracked objects into a desired pose relative to a body part, comprising:

at least one tracked object;

a localizing device for measuring the pose of the at least one tracked object, said localizing device comprising two or more sensor units, each with an associated coordinate frame and comprising a plurality of individual sensor elements, each sensor unit being capable of providing sufficient data to permit the calculation of the pose of the at least one tracked object;

means for determining the pose of the tracked object based on the data from one or more sensor units; and

means for determining the relationship among the coordinate frames of the sensor units.

26. The computer assisted surgery system of

claim 25

wherein the means for determining the relationship among coordinate frames of the sensor units is a registration object whose pose is measured by the sensor units.

27. The computer assisted surgery system of

claim 25

wherein the pose of a first tracked object is determined from data from a first sensor unit, and the pose of a second tracked object is determined from data from a second sensor unit.

28. The computer assisted surgery system of

claim 27

wherein a surgical drape is positioned between the first and second tracked objects.

29. The computer assisted surgery system of

claim 28

wherein the first tracked object is outfitted with a plurality of localizing emitters, which are measured by the first sensor unit only when one or more of the localizing emitters on the first tracked object is activated, and the second tracked object is outfitted with a plurality of localizing emitters, which are measured by the second sensor unit only when one or more of the localizing emitters on the second tracked object is activated, and the one or more localizing emitters of only one tracked object are activated at a time.

30. The computer assisted surgery system of

claim 25

wherein the pose of a tracked object is determined from simultaneous data from more than one sensor unit.

31. The computer assisted surgery system of

claim 25

wherein the pose of a tracked object is determined from data from a first sensor unit, a second sensor unit, or simultaneous data from both sensor units depending on whether the object is in the field of view of the first sensor unit, the second sensor unit, or both sensor units, respectively.

32. The computer assisted surgery system of

claim 31

wherein one or more sensor elements of the sensor units are mounted on the ceiling of an operating room.

33. A method for determining the pose of a surgical tool relative to an imaging device wherein the surgical tool is located on one side of a surgical drape and the imaging device is located on the other side of the surgical drape, comprising the steps of:

providing a localizing device with two or more sensor units, each sensor unit having a coordinate frame;

positioning a registration object such that its pose may be measured by at least a first sensor unit and a second sensor unit;

using at least the first sensor unit to measure the pose of the registration object relative to the coordinate frame of said first sensor unit;

using at least the second sensor unit to measure the pose of the registration object relative to the coordinate frame of said second sensor unit;

calculating the relationships among the coordinate frames of at least the first and second sensor units;

placing a surgical drape between the imaging device and the surgical tool, such that the first sensor unit is able to measure the pose of imaging device on a first side of the surgical drape, and the second sensor unit is able to measure the pose of the surgical tool on a second side of the surgical drape; and

using the previously calculated relationships among the coordinate frames of at least the first and second sensor units to calculate the pose of the surgical tool relative to the imaging device.

34. A method for measuring the pose of a tracked object located on either side of an obstructing object, comprising the steps of:

providing a localizing device with two or more sensor units, each sensor unit having its own coordinate frame;

selecting the coordinate frame of one of the two or more sensor units as a reference coordinate frame;

placing a registration object in view of all of the two or more sensor units;

using each of the sensor units to measure the pose of the registration object relative to that sensor unit'"'"'s coordinate frame;

calculating the relationships among the coordinate frames of all sensor units;

placing the obstructing object such that the first sensor unit is able to measure the pose of a tracked object on a first side of the obstructing object, and the second sensor unit is able to measure the pose of a tracked object on a second side of the obstructing object;

placing the tracked object in the view of at least one sensor unit and measuring its pose with said sensor unit; and

using the previously calculated relationships among the coordinate frames of the sensor units to calculate the pose of the tracked object relative to the reference coordinate frame.

35. An image guided surgery system to enable a surgeon to move a surgical tool into a desired pose relative to an object, comprising:

an imaging device for generating a plurality of two-dimensional images of the object, a localizing device for determining the pose of the surgical tool and the pose of the imaging device;

a stored computer model of the object;

means for determining the pose of the object;

means for displaying a representation of the surgical tool relative to the two-dimensional images of the object; and

means for displaying a representation of the surgical tool relative to the computer model of the object;

wherein the computer model of the object is projected onto a picture plane that is oriented so as to provide a view of the object distinct from the views represented by the two-dimensional images.

36. The image guided surgery system of

claim 35

wherein two of the two-dimensional images generated by the imaging device represent substantially orthogonal views, and wherein the picture plane for projection of the computer model of the object represents a view substantially orthogonal to said two-dimensional images.

37. The image guided surgery system of

claim 35

wherein the object is a second surgical tool and the means for determining the pose of said second surgical tool is a localizing device.

38. The image guided surgery system of

claim 37

wherein the second surgical tool is a device for tracking the pose of an implant and the computer model of the object comprises a representation of the implant.

39. The image guided surgery system of

claim 38

wherein the implant is an intramedullary rod and the picture plane is oriented approximately perpendicular to its long axis so as to cause to be displayed a cross sectional representation of said intramedullary rod.

40. A method for verifying the accuracy with which an image guided surgery system displays a representation of a surgical tool relative to image data comprising the steps of:

providing a localizing device;

positioning a surgical tool such that an imaging device may acquire an image of the surgical tool;

acquiring an image of the surgical tool with the imaging device and using the localizing device to read the pose of the surgical tool relative to the imaging device;

recording said pose of the surgical tool relative to the imaging device;

displaying the image of the surgical tool;

calculating the position of the representation of the surgical tool relative to the image of the surgical tool based on the recorded pose of the surgical tool relative to the imaging device;

retaining the surgical tool representation overlaid on the surgical tool image for a period of time sufficient for the surgeon to determine the accuracy of the positioning of the surgical tool representation relative to the image of the surgical tool.

41. An image guided surgery system for positioning a surgical tool relative to a body part comprising:

an optical localizer;

a C-arm fluoroscope with an attached housing that contains localizing emitters;

one or more surgical tools;

a display means for displaying a representation of the surgical tool relative to images of the body part; and

a sterile surgical drape, a section of the drape being adapted to cover the housing containing the localizing emitters, a portion of said section of the drape further adapted to fit flush and flat against the localizing emitters.

42. The image guided surgery system of

claim 41

wherein the portion of the sterile drape fitting flush and flat against the localizing emitters is similar in dimension to the housing containing the localizing emitters.

43. The sterile drape of

claim 42

further comprising a retaining ring that holds the drape against the housing and causes the drape to fit flush and flat against the localizing emitters.

44. A surgical drape for covering a fluoroscopic imaging device containing a plurality of localizing emitters, said drape comprising a section for covering the part of the fluoroscopic imaging device containing the plurality of localizing emitters, a portion of said section further adapted to fit flush and flat against the localizing emitters.

45. The surgical drape of

claim 44

further comprising a retaining ring that holds the drape against the housing and causes the drape to fit flush and flat against the localizing emitters.